Tag Archives: Dark Matter

Part 6 of my review of the book: “The Big Picture: On the Origins of Life, Meaning and the Universe Itself,” by Sean M. Carroll. Part 5 is found here.

The Core Theory

Carroll spends several chapters discussing the quantum mechanical framework for the Core Theory, as he calls it. Quantum mechanics has been an extremely successful physical theory exquisitely predicting with enormous precision some parameters in particle physics. But what many people have heard of quantum theory is more about the various interpretations applied by physicists (e.g. Bohr’s abstract physical description, or, Everett’s many-worlds) to the way the theory might work beneath what we can measure.

Regardless of the correct interpretation it has enjoyed enormous success as a theory of physics in what is called the standard model of particle physics. The second very successful theory is general relativity—Einstein’s theory of gravity. Both work extremely well in their respective domains of operation, but outside that, in the realm of what is called quantum gravity neither operate nor has a theory been found to unite them. But that is exactly what Stephen Hawking and others have been seeking, to have the Universe begin in a quantum fluctuation of a meta-stable false vacuum.

But even though we have this limitation, in the realm of what humans can measure, Carroll has faith and writes:

“What we can do is show that physics by itself is fully up to the task of accounting for what we see.” (p.179)

However he admits that one class of particles not part of the current Core Theory are those that make up “dark matter” in the Universe. Such alleged weakly interacting putative particles are allowed for in the Core Theory because they are so weakly interacting with normal atomic matter that they are hard to detect. I would argue that dark matter and other dark entities are a philosophical construct used to keep the standard big bang cosmology from being discredited.1 Dark matter was first needed to explain the dynamics of spiral galaxies. Now it seems that it is no longer needed, when standard physics is applied correctly.2Continue reading →

Dark matter has been detected: neutrinos fit the definition of Weakly Interacting Massive Particles, as they have such small probabilities of interacting with atomic matter that it takes several moles of neutrinos to achieve the same probability of a single interaction as a single neutron or photon. Though individually nearly massless and invisible to matter, the sheer number of neutrinos surrounding us makes it possible to detect them, and makes their combined energy a significant component of the mass of the Universe.

Likewise, Massive Compact Halo Objects are quite ordinary matter. They are planetary and sub-planetary bodies, producing little or no light, and so hard to detect. To these, we add black holes, neutron stars, and brown dwarfs, which also emit little or no light, despite their mass.

Neither should the existence of dark energy be any surprise to Christians. After all, the Bible say, “The heavens are stretched out like a curtain.” Dark energy is the energy of the vacuum state, less than 1 microjoule per cubic meter, distributed uniformly. Only because of the vastness of space are we able to observe its effects. Even so, were this tremendous amount of energy somehow liberated, “the elements shall be consumed by fire.” The decay of the vacuum state, unleashing the tremendous amount of energy stored in it, could very well be the means by which the Lord transforms the Universe at the end of the age.

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There was talk over lunch and coffee of dark forces, dark photons, and dark neutrons.1 (emphasis added)

This is the extent of what is actually known about dark matter and any other entities from the dark sector of particle physics. At a workshop where more than 100 physicists took over the University of Maryland, titled “US Cosmic Visions: New Ideas in Dark Matter,” attendees were encouraged to think more broadly to solve the vexing problem of the non-detection of dark matter particles in all experiments that have ever been tried for the last 40 years, at least.

They spoke of axions and other dark-matter candidates so lightweight that they would be detected as waves, and of particles so heavy that they would clump together and encounter Earth only occasionally as a vast invisible glob.1

Despite impressive sensitivity, dark-matter detection experiments such as Large Underground Xenon (detector array above) have not found any evidence of WIMPs. Credit: C. H. Faham/LUX

A recalibration for the dark-matter community

For decades physicists have been fixated on the putative WIMP, a Weakly Interacting Massive Particle, which allegedly has a tendency to intermittently mingle with ordinary matter via the weak force. WIMPs have been alleged to inhabit our part of the Galaxy but all experiments, like the Large Underground Xenon (LUX) detector array, have failed to find any trace of their existence. Theorists developed ideas that WIMPs might be the lowest mass yet stable supersymmetric particle, called the neutralino but experimentalists with vast, exquisitely sensitive underground detectors such as the LUX array or using the powerful particle accelerator the Large Hadron Collider (LHC) found no such particles though they were meant to be constantly streaming stealthily through our planet. Now, Continue reading →

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Unseen dark matter has been invoked several times to solve problems in astrophysics and cosmology. Historically the most significant problem has been the rotation curves of galaxies, particularly spiral galaxies. Using the Doppler Effect the speeds of the stars and gases in the disk regions of spiral galaxies can be measured. See Fig. 1.

By now hundreds of thousands of galaxies have been measured this way. What is observed is that the speeds of the stars, and the gases beyond where the stars are observed, are much greater than it would appear Newtonian physics allows for.

Figure 1: Edge on spiral galaxy and a rotation curve. Speeds of stars measured from the centre of a galaxy like this, as a function of distance in light-years. Using carbon-monoxide (CO) as a tracer gas the speeds of gas in the rotating disk can be also measured where there are no visible stars (labelled “No Stars”).

As a result it has been suggested that there is an invisible halo of cold non-interacting matter. This putative invisible halo has the needed gravitational effect on the stars and gases but it cannot be seen, hence it is called dark matter. Dark matter is alleged not to be normal atomic matter, made from protons and neutrons (which are known as baryons), but some sort of slowly moving (cold) exotic non-baryonic matter. Weakly Interacting Massive Particles (WIMPs) were suggested. Continue reading →

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Awhile ago I wrote about Lisa Randall, Professor of Science at Harvard University, a theoretical physicist and cosmologist, who proposed that the dinosaurs went extinct due to the actions of unseen dark matter.¹ There now appears again an article in the popular science magazine Nautilus with the title “Does Dark Matter Harbor Life? An invisible civilization could be living right under your nose.”² It would appear to be excerpted from Randall’s book Dark Matter and the Dinosaurs. In the article Randall asserts that we may, in fact, be kind of racist against dark matter, well, at least, we are biased towards ordinary matter, where, she claims, in fact, that dark matter is the stuff that holds galaxies together so it is really important stuff.

The common assumption is that dark matter is the “glue” that holds together galaxies and galaxy clusters, but resides only in amorphous clouds around them. But what if this assumption isn’t true and it is only our prejudice—and ignorance, which is after all the root of most prejudice—that led us down this potentially misleading path?

People in foreign relations make a mistake when they lump together another country’s cultures—assuming they don’t exhibit the diversity of societies that is evident in our own. Just as a good negotiator doesn’t assume the primacy of one sector of society over another when attempting to place the different cultures on equal footing, an unbiased scientist shouldn’t assume that dark matter isn’t as interesting as ordinary matter and necessarily lacks a diversity of matter similar to our own.² (emphasis added)

She goes on to promote the possibility of dark life, invisible creatures living on dark planets around dark stars in dark parts of galaxies. She suggests dark matter may be much more than just amorphous matter, but have a rich life with dark forces and therefore this implies a dark invisible universe of creatures we cannot detect. Sure sounds like good material for a sci-fi story.

Partially interacting dark matter certainly makes for fertile ground for speculation and encourages us to consider possibilities we otherwise might not have. Writers and moviegoers especially would find a scenario with such additional forces and consequences in the dark sector very enticing. They would probably even suggest dark life coexisting with our own. In this scenario, rather than the usual animated creatures fighting other animated creatures or on rare occasions cooperating with them, armies of dark matter creatures could march across the screen and monopolize all the action.

But this wouldn’t be too interesting to watch. The problem is that cinematographers would have trouble filming this dark life, which is of course invisible to us—and to them. Even if the dark creatures were there (and maybe they have been) we wouldn’t know. You have no idea how cute dark matter life could be—and you almost certainly never will.

Though it’s entertaining to speculate about the possibility of dark life, it’s a lot harder to figure out a way to observe it—or even detect its existence in more indirect ways. It’s challenging enough to find life made up of the same stuff we are, though extrasolar planet searches are under way and trying hard. But the evidence for dark life, should it exist, would be far more elusive even than the evidence for ordinary life in distant realms.

Dark objects or dark life could be very close—but if the dark stuff’s net mass isn’t very big, we wouldn’t have any way to know. Even with the most current technology, or any technology that we can currently imagine, only some very specialized possibilities might be testable. “Shadow life,” exciting as that would be, won’t necessarily have any visible consequences that we would notice, making it a tantalizing possibility but one immune to observations. In fairness, dark life is a tall order. Science-fiction writers may have no problem creating it, but the universe has a lot more obstacles to overcome. Out of all possible chemistries, it’s very unclear how many could sustain life, and even among those that could, we don’t know the type of environments that would be necessary.² (emphasis added)

Occasionally we read in the popular press, especially online, that someone has come up with a new theory of gravity. Why is that even necessary if the current theory describing the evolution of the universe is so correct?

The standard ΛCDM big bang cosmology is derived from an application of certain non-biblical boundary conditions to the physics of Einstein’s general relativity theory. But when that was applied to the universe as a whole, two problems developed for the secular model. One is the need to add in dark energy (or the cosmological constant, Λ (Lambda), to Einstein’s field equations) and the other is the need for a significant amount of invisible cold dark matter (CDM).

On the scale of galaxies and even clusters of galaxies Newtonian physics is used as it is the low gravity limit of general relativity. But without the addition of dark matter the resulting theory, using the known density of visible matter in galaxies (see Fig. 1) and clusters, does not match observations. But for more than 40 years now dark matter has been sought in various lab experiments with consistently negative results. This has developed into what is called the dark matter crisis.1

Figure 1: Typical rotation curve of a spiral galaxy: Speeds (V) in km/s units as a function of distance from the centre of the galaxy (R) in 1000 light-year (ly) units. The upper curve shows the speeds of the stars in disk region determined from their visible light and the gasses beyond that determined from radio frequency emissions. The lower curve shows what standard Newtonian physics predicts should be observed. The discrepancy is made up by positing the existence of invisible dark matter. Credit: Wikipedia

Occasionally a claim is made that a theorist has some inkling of what dark matter particles might be but the crisis remains.2 Dark matter particles have been sought without success in the Galaxy using very sensitive detectors deep in underground mines,3 or with the Large Hadron Collider (LHC) over 10 years of experiments looking for the lowest mass stable particle in a theorised class of as-yet-undiscovered supersymmetric particles.4

The observational data from thousands of galaxies together with the negative outcome of all the experiments searching for Dark Matter particles indicate that either something is wrong with the physics we use or that the expected dark matter is much more elusive than supposed, or, indeed, does not, in fact, exist—which gets us back to something being wrong with the physics. Continue reading →

Dark matter has been invoked to solve many vexing problems in astrophysics and cosmology.1 Now it seems it has been invoked to solve the evolutionists’ problem of extinction of the dinosaurs.2

Lisa Randall Credit: Wikipedia Public Domain

American theoretical physicist and cosmologist Dr Lisa Randall has developed a breakthrough five dimensional warped geometry theory. About two years ago she proposed a new hypothesis on dark matter which suggests the mysterious invisible substance that allegedly dominates the universe played a role in killing the dinosaurs.3 She even has written a book on it—Dark Matter and the Dinosaurs. In the book her new theory is summarised as follows.

[A]bout 66 million years ago, gravitational perturbations caused by a thin pancake-shaped disc of dark matter in the Milky Way galaxy dislodged icy comets in the Oort cloud at the very edge of the known solar system, resulting in the fiery meteoroid that eventually crash-landed in the Yucatan, leading to the mass extinction of more than 75 per cent of life on the planet in the process.3

Her radical new theory even posits mass extinctions every 35 million years or so.

“I am fully aware that it is speculative,” she says.4

Dinosaurs sell books and she has written a book that needs to be sold.

I’d call it a fairytale, except that might be insulting to fairies. To believe that it could even be true takes a lot of faith, which apparently describes Randall. She is reported to be unfazed by the panoply of uncertainties that her new theory incorporates.4Continue reading →